Investigation of cracked reinforced concrete framed structures repaired with CFRP

According to Urban Renewal Authority, out of the existing 8,500 urban buildings, which are over 30 years old, some 6,100 require extensive repairs or repairs of varying scale. In 10 years' time, the number of buildings over 30 years old will increase by 50%. Structural repairing/retrofitting is achieving more and more attention over the past decades because of the advancement in material and the high demand on repair works. Among all the retrofitting materials, carbon fiber reinforced plate is the most widely used one owning to its high strength and lightweight. Over the past years, many researches have been done on the material properties of CFRP. However, most of the tests are based on small-scale uncracked single beams or columns. The actual performance of these retrofitting material on large-scale, cracked structures is still unknown, which is the main reason limiting the use of these materials. In this research, a proposed probability-based effective stiffness model was used to calculate the effective stiffness of each structural member in a frame structure after cracking. This model was modified and was used to calculate the improvement in stiffness for each structural member after retrofitting with CFRP. This study indicated that the proposed iterative method could predict the lateral deflection of reinforced concrete structures in a more direct and accurate manner. There recorded a less than 5% error in lateral deflection for beam structure and less than 8% error for frame structure. Two repairing configuration is proposed to repair the rigid frame structure. The significant reduction is lateral deflection after each repairing stage reflected that both repairing configuration can effectively improve the serviceability performance of frame structure. The overall percentage reduction in lateral deflection is 30.81% after 6 stages of repairing. The study also suggested that more research on the push-and-pull dynamic effect on CFRP repaired members and the anchorage zone design near the joint is needed before the repairing technique can readily put into practices